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#1 Flummoxed

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Posted 01 May 2020 - 05:51 AM

due to the following link being posted in recent science news ref lightning https://www.discover...tent=FeedBurner

 

I would like to pose a speculative question. The mechanism by which charge builds up in a thundercloud is considered to be by collision of ice particles formed in clouds, lightning mostly starts in the evening especially around the equator +/-15degrees. http://www.planet-sc...-lightning.aspx

 

https://en.wikipedia...osphere#D_layer

The ionosphere is normally considered to start at around 60km height, I can find no references to convection currents in the ionosphere bringing this ionized layer of gas down to the level of the top of a thunder cloud which reaches typically 20km high. Is it possible that the ionosphere experiences convection currents especially over the top of cumulus thunder clouds which brings the ionospheric charge down to the cloud charging it. https://www.nssl.noa...ightning/types/ Clearly some lightning effects do affect the ionosphere, could the ionosphere be the primary charging effect in a cloud rather than colliding ice particles?

 

How much charge could the ionosphere provide to a thundercloud if the two were to make contact.?


Edited by Flummoxed, 01 May 2020 - 05:58 AM.


#2 LaurieAG

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Posted 01 May 2020 - 11:00 PM

Sprites might have something to do with it although they aren't exactly lightning themselves.

 

https://en.wikipedia...ite_(lightning)



#3 Flummoxed

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Posted 02 May 2020 - 04:16 AM

Sprites might have something to do with it although they aren't exactly lightning themselves.

 

https://en.wikipedia...ite_(lightning)

 

Do sprites move up from the cloud or down from the ionosphere? 



#4 Flummoxed

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Posted 02 May 2020 - 04:21 AM

One thing I wondered about many years ago when I was clever, was could the differing work functions of ice and water in a thunder cloud be responsible for the charge build up rather than friction as popularly suggested. I just dug up this paper which suggests this might be a plausible mechanism. https://agupubs.onli...JD090iD04p06041 Perhaps I was right back then.

 

"

       

Abstract

Laboratory experiments measuring the charge transferred when individual 100‐μm ice spheres impact upon various metal targets show that the charge transferred depends upon the work function of the metal. If ice is assigned a “work function” of 4.3 eV, then the contact potential difference between the ice and the metal accounts for the observed charging. It may be possible to explain the generation of charge within thunderstorms in terms of a contact potential difference between colliding vapor‐grown crystals and riming hailstones. Although many experiments measuring the charging of ice from collisions can be explained in terms of contact potentials, we report one that cannot. A layer of ice estimated to be 1 μm thick deposited from the vapor (“frost”) on the target is sufficient to cause it to charge positively, and conversely, if a similar thickness is allowed to evaporate, the target reverts to negative charging.

"


Edited by Flummoxed, 02 May 2020 - 04:22 AM.


#5 OceanBreeze

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Posted 02 May 2020 - 05:07 AM

due to the following link being posted in recent science news ref lightning https://www.discover...tent=FeedBurner

 

I would like to pose a speculative question. The mechanism by which charge builds up in a thundercloud is considered to be by collision of ice particles formed in clouds, lightning mostly starts in the evening especially around the equator +/-15degrees. http://www.planet-sc...-lightning.aspx

 

https://en.wikipedia...osphere#D_layer

The ionosphere is normally considered to start at around 60km height, I can find no references to convection currents in the ionosphere bringing this ionized layer of gas down to the level of the top of a thunder cloud which reaches typically 20km high. Is it possible that the ionosphere experiences convection currents especially over the top of cumulus thunder clouds which brings the ionospheric charge down to the cloud charging it. https://www.nssl.noa...ightning/types/ Clearly some lightning effects do affect the ionosphere, could the ionosphere be the primary charging effect in a cloud rather than colliding ice particles?

 

How much charge could the ionosphere provide to a thundercloud if the two were to make contact.?

 

Thunderstorm, cumulonimbus clouds form due to a temperature differential between hot ground and cooler air high above. The air near to the ground is heated during the day and warm air then rises, carrying a lot of water vapor up with it. As the warm air gets higher, it cools, condenses and reaches saturation whereupon the water vapor separates into an aerosol of tiny droplets and ice particles. It is the static electricity generated by these particles that build up the electrical potential for lightning.

 

Even the largest supercell thunderstorm clouds reach “only” to 75,000 feet (23 km), while the lowest layer of the ionosphere (D layer) dips down to around 60 km, and that layer exists only during the day as it is created by solar radiation.

 

It would seem then that the ionosphere cannot be playing much of a role, if any, in charging the thunder clouds.

 

Also, I am not even sure your statement “lightning mostly starts in the evening especially around the equator” is correct, but even if true, it would seem to contradict the idea of the ionosphere playing a role since at night the D layer doesn’t exist. The lowest layer at night is the E layer at around 100 km, far above even the highest thunder clouds.


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#6 OceanBreeze

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Posted 02 May 2020 - 05:10 AM

One thing I wondered about many years ago when I was clever, was could the differing work functions of ice and water in a thunder cloud be responsible for the charge build up rather than friction as popularly suggested. I just dug up this paper which suggests this might be a plausible mechanism. https://agupubs.onli...JD090iD04p06041 Perhaps I was right back then.

 

"

       

Abstract

Laboratory experiments measuring the charge transferred when individual 100‐μm ice spheres impact upon various metal targets show that the charge transferred depends upon the work function of the metal. If ice is assigned a “work function” of 4.3 eV, then the contact potential difference between the ice and the metal accounts for the observed charging. It may be possible to explain the generation of charge within thunderstorms in terms of a contact potential difference between colliding vapor‐grown crystals and riming hailstones. Although many experiments measuring the charging of ice from collisions can be explained in terms of contact potentials, we report one that cannot. A layer of ice estimated to be 1 μm thick deposited from the vapor (“frost”) on the target is sufficient to cause it to charge positively, and conversely, if a similar thickness is allowed to evaporate, the target reverts to negative charging.

"

 

Unfortunately, the paper you cite, from 1985, is not open access.

 

Here is an interesting, open access paper from 2003, that describes the charging process that takes place in thunderstorms: “when mm-sized ice particles formed from accreted supercooled drops, hereafter graupel, fall at speeds exceeding 5 m s−1 and strike small, uplifting ice crystals (Illingworth, 1985). About 20 fC per collision is transferred from one to the other, leading to powerful in-cloud electric fields and often lightning, thus maintaining Earth’s electrical circuit”

 

Lightning is interesting, and not fully understood.



#7 Flummoxed

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Posted 02 May 2020 - 01:08 PM

Unfortunately, the paper you cite, from 1985, is not open access.

 

Here is an interesting, open access paper from 2003, that describes the charging process that takes place in thunderstorms: “when mm-sized ice particles formed from accreted supercooled drops, hereafter graupel, fall at speeds exceeding 5 m s−1 and strike small, uplifting ice crystals (Illingworth, 1985). About 20 fC per collision is transferred from one to the other, leading to powerful in-cloud electric fields and often lightning, thus maintaining Earth’s electrical circuit”

 

Lightning is interesting, and not fully understood.

 

I was right all those years ago, the charge has little or nothing to do with friction. Speed of impact, temperature, and size of ice crystals or particulates are what causes the charge build up. Would you agree the charge build up is due to different work functions or not? 

 

I agree, Lightning does happen at different times of day, other than just after sunset near the equator. What I observed crossing the Atlantic, Pacific and Indian Oceans is that almost without fail cumulus builds during the day, and the lightning starts just after it gets dark. It is usually is over in about 2-3 hours, when the clouds all usually disperse leaving the sky clear and full of stars, unless there is bad weather :) 



#8 LaurieAG

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Posted 02 May 2020 - 10:09 PM

Do sprites move up from the cloud or down from the ionosphere? 

 

Sprites or red sprites are large-scale electrical discharges that occur high above thunderstorm clouds, or cumulonimbus, giving rise to a quite varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground.

Sprites appear as luminous reddish-orange flashes. They often occur in clusters above the troposphere at an altitude range of 50–90 km (31–56 mi). Sporadic visual reports of sprites go back at least to 1886[1] but they were first photographed on July 6, 1989, by scientists from the University of Minnesota and have subsequently been captured in video recordings many thousands of times.

Sprites are sometimes inaccurately called upper-atmospheric lightning. However, sprites are cold plasma phenomena that lack the hot channel temperatures of tropospheric lightning, so they are more akin to fluorescent tube discharges than to lightning discharges. Sprites are associated with various other upper-atmospheric optical phenomena including blue jets and ELVES.[1]

 



#9 Flummoxed

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Posted 03 May 2020 - 03:12 AM

 

 

Hi Laurie

 

The light show from sprites is most likely caused by ions recombining or returning to their ground state after being excited in the atmosphere giving of photons with a reddish orange colour which would indicate a gas  made of ???????? http://chemed.chem.p..._pages/6.5.html Helium

 

Why would a lightning strike to ground 40km below trigger ions to recombine in the troposphere ? I have heard if you point a Radar at a disconnected fluorescent tube it will light up. I would "guess" since sprites are a cold plasma, the electromagnetic wave travelling up from the thundercloud is ionizing helium gas in the troposhere, since helium is less prevalent at lower altitudes sprites do not occur directly above a thundercloud.

 

The ionosphere is not responsible for the charging of thunderclouds. Sprites are a result of an electromagnetic wave from a lightning strike to ground causing the atmosphere to fluoresce. 



#10 Flummoxed

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Posted 03 May 2020 - 03:19 AM

https://en.wikipedia.../Ball_lightning

 

Does anyone have opinions on what a lightning ball consists off ????

Are they a Hot or Cold Plasma, of ionized gases???????

 

What do those ionized gases consist off ?????? 



#11 OceanBreeze

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Posted 03 May 2020 - 04:24 AM

I was right all those years ago, the charge has little or nothing to do with friction. Speed of impact, temperature, and size of ice crystals or particulates are what causes the charge build up. Would you agree the charge build up is due to different work functions or not? 

 

 

 

 

I might have agreed to that prior to reading the paper I have referenced in my last post, but not after having read through it in some detail.

 

I do agree that in the usual case of contact charging, charges are exchanged between the objects in proportion to the difference between the effective work functions associated with the two (different) materials.

 

However, in the thunderstorm cloud, we are talking about a mixture of a materials, ascending ice crystals and descending graupel; both forms of the same fundamental substance H2O, and therefore they must have nearly the same chemical composition and presumably the same value of effective work function.

 

This paper argues that there is an “unusual property of charging during ice-ice collisions” which arises “from a primarily one-way transfer of charged melt” which differs from the usual case of contact charging.

 

The authors claim during a net transfer of electric charge in ice-ice collisions, there is “mass and charge transfer from the corner of a facetted crystal to the underside of sublimating graupel”

 

graupel-microscope.jpg

 

 

When an ice crystal lattice is formed, H2O undergoes a proton shift along a hydrogen bond, creating -OH and +H3O ions and “the effective charge of OH− in ice, qOH, is charge −0.62e, not e” (I am not 100% clear on why the effective charge is −0.62e, and not e. I need to read up on that but it is suggestive of something to do with time constants)

 

So, before the collision with the graupel, the crystal surface has OH− charge. “The collision squeezes this charged mass into melt on the underside of the graupel, that is pushed outward from a thin region between the ice particles and then freezes onto the graupel”

 

Bottom line is the mass transfer from crystal to graupel also transfers some electric charge to the graupel.

 

The rest of the paper goes into detail about the other variables involved such as temperature and collision velocity, with all the relevant mathematics. It is all interesting, depending on how deep you want to delve into it and how much more time you need to spend in lockdown.

 

 

I agree, Lightning does happen at different times of day, other than just after sunset near the equator. What I observed crossing the Atlantic, Pacific and Indian Oceans is that almost without fail cumulus builds during the day, and the lightning starts just after it gets dark. It is usually is over in about 2-3 hours, when the clouds all usually disperse leaving the sky clear and full of stars, unless there is bad weather :)

 

 

 

I too, have sailed the oceans blue, and have experienced many lightning and thunder storms mostly around mid-day in the tropics.  Lightning is most pronounced at night, for obvious reasons, but anecdotally at least, I don't believe it happens more frequently at night.



#12 Flummoxed

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Posted 03 May 2020 - 10:48 AM

I might have agreed to that prior to reading the paper I have referenced in my last post, but not after having read through it in some detail.

 

I do agree that in the usual case of contact charging, charges are exchanged between the objects in proportion to the difference between the effective work functions associated with the two (different) materials.

 

However, in the thunderstorm cloud, we are talking about a mixture of a materials, ascending ice crystals and descending graupel; both forms of the same fundamental substance H2O, and therefore they must have nearly the same chemical composition and presumably the same value of effective work function.

 

This paper argues that there is an “unusual property of charging during ice-ice collisions” which arises “from a primarily one-way transfer of charged melt” which differs from the usual case of contact charging.

 

The authors claim during a net transfer of electric charge in ice-ice collisions, there is “mass and charge transfer from the corner of a facetted crystal to the underside of sublimating graupel”

 

graupel-microscope.jpg

 

 

When an ice crystal lattice is formed, H2O undergoes a proton shift along a hydrogen bond, creating -OH and +H3O ions and “the effective charge of OH− in ice, qOH, is charge −0.62e, not e” (I am not 100% clear on why the effective charge is −0.62e, and not e. I need to read up on that but it is suggestive of something to do with time constants)

 

So, before the collision with the graupel, the crystal surface has OH− charge. “The collision squeezes this charged mass into melt on the underside of the graupel, that is pushed outward from a thin region between the ice particles and then freezes onto the graupel”

 

Bottom line is the mass transfer from crystal to graupel also transfers some electric charge to the graupel.

 

The rest of the paper goes into detail about the other variables involved such as temperature and collision velocity, with all the relevant mathematics. It is all interesting, depending on how deep you want to delve into it and how much more time you need to spend in lockdown.

 

 

 

 

I too, have sailed the oceans blue, and have experienced many lightning and thunder storms mostly around mid-day in the tropics.  Lightning is most pronounced at night, for obvious reasons, but anecdotally at least, I don't believe it happens more frequently at night.

 

Normally in the tropics Cumulus build during the day, and disperse over night. At the end of the day they are the biggest, and at sunset and just after lightning is more noticeable. When I sailed just northern waters, I would agree lightning does not appear to have a preferred time of day, but in warmer climates it does seem too. The Biggest lightning strikes appear to happen down wind from active Volcanoes in my experience, skyscrapers coming to ground!

 

I have a blank spot in my brain when it comes to Chemistry, but I understand(used too) a bit about semi conductors and electron hole pairs. It strikes me that the ice crystals are momentarily making a semiconductor like junction and allowing a charge transfer https://www.europhys...19881905p61.pdf I think the paper is stating the same thing as your paper.

 

What is your opinion on lightning balls ? Plasma or particles of what, electrons and positrons, quarks maybe ions. The reason I mention positrons is that lightning has now been proven to produce positrons, and anecdotal evidence has balls of lightning passing through walls, I dont see how a particle can easily do that.



#13 OceanBreeze

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Posted 04 May 2020 - 03:19 AM

What is your opinion on lightning balls ? Plasma or particles of what, electrons and positrons, quarks maybe ions. The reason I mention positrons is that lightning has now been proven to produce positrons, and anecdotal evidence has balls of lightning passing through walls, I dont see how a particle can easily do that.

 

Well, it seems these things do exist and there are several possible explanations.

I think these phenomena might be what this paper terms “whistlers”.


Edited by OceanBreeze, 04 May 2020 - 03:20 AM.


#14 Flummoxed

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Posted 04 May 2020 - 04:01 AM

Well, it seems these things do exist and there are several possible explanations.

I think these phenomena might be what this paper terms “whistlers”.

 

Whistlers sound a bit speculative and dont explain how they might pass through walls.

 

We know now, which they did not know in 1999 when the paper was written, that lightning can produce positrons in the top of lightning clouds which are blasted out into space. https://www.nasa.gov...nderstorms.html  Also understanding this gives a better under standing of how TGF's Terrestrial Gamma Ray Flashes work, not explained in your paper. 

 

When a bolt of lightning follows the feeder to ground. It is normally seen to terminate instantly from cloud to ground.  But when the connection is broken leaving large amounts of plasma in the air, the plasma might pool in a similar way to positive lightning. 

 

Positive strikes to ground known as bolts from the blue. move horizontally away from the clouds stopping pooling and moving on again before eventually coming to ground, miles from the lightning cloud which can be over the horizon, hence bolts from a blue sky.

 

Looking at how positrons may be formed in thunderclouds is it beyond the realms of possibility that a positron electron plasma might form, which being electrically conductive might pass through walls???????????



#15 Flummoxed

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Posted 05 May 2020 - 02:41 AM

How would anyone like a gargantuan hail stone on your head or through your windscrene https://phys.org/new...weekly-nwletter

 

The anvil shape of thunderclouds is interesting especially around volcanoes https://www.physicsf...-rising.988351/